Patent GB-1177263-A (GB)
Title: Improvements in or relating to Hydromechanical Differential Type Gearbox
Inventor: HAU ANTONIN
IPC: F16H3/44
Filed: 1967-03-28
Abstract: 1,177,263. Hydro-mechanical variable-speed gear. USTAV PRO VYZKUM MOTOROVYCH VOZIDEL. 28 March, 1967 [29 March, 1966], No. 13955/67. Heading F2D. In an hydromechanical variable-speed gear for a motor vehicle, comprising a hydrodynamic torque converter and a junction planetary gear set 9, 13, 15 re-uniting split torques ofthe mechanical and hydraulic branches, a second reduction planetary gear set 6, 8, 10 is included in the hydraulic branch and is driven by the turbine 3. As shown, first forward speed of four forward speed and reverse gear is established by disengaging converter by-pass clutch 18 and engaging blocking clutch 22 for the junction gear set, the entire torque passing through the torque converter. Split torque second is engaged by engaging clutch 18 and a brake 11 to hold the ring gear 10 and disengaging the clutch 22. Split torque third is established by engaging clutch 12 between ring gear 10 and output shaft 14, a free-wheel 21 being between the ring gear 10 and brake 11. If the clutch 12 and brake 11 are actuated simultaneously the free-wheel may be omitted. An all-mechanical direct drive third may be established by the simultaneous engagement of clutches 18 and 22. Reverse is established by engaging a brake 20 to hold carrier 8 and clutch 12, and disengaging clutches 18, 22 and brakes 11 and 19, the entire torque again being transmitted through the torque converter. Utilization of the torque converter as a decelerating brake, with brake 19 engaged to hold turbine 3, is obtained in three stages: (a) with blocking clutch 22 and clutch 18 engaged, and brakes 20 and 11 disengaged, the direct drive is engaged and the entire torque is transmitted to the engine and impeller 2 directly by shaft 16; (b) more intensive braking is obtained by disengaging blocking clutch 22 and engaging clutch 12 when the breaking torque is transmitted to the carrier 13 of the junction gear set and, via clutch 12, ring gear 10, carrier 8, to its ring gear 9; (c) the most intensive braking is obtained by simultaneously engaging brakes 19 and 20 while disengaging clutches 12 and 22, braking torque being transmitted to the carrier 13 and hence shaft 16, the overrun ratio being determined by the ratio between carrier 13 and sun gear 15. Again, Fig. 1 (not shown), the by-pass clutch 18, brake 19, brake 20, free-wheel 21, and blocking clutch 22 are all omitted, split torque first being established by engaging brake 11, and split torque second by releasing brake 11 and engaging clutch 12. In Fig. 2 (not shown), both gear sets of the Figure 1 embodiment are provided with stepped planets and additional integral sun gears (8), (9), the junction gear set having no ring gear. Split torque first is again established by engaging brake 11 to hold the carrier (17) of the second reduction planetary gear set, and split torque second is established by disengaging brake 11 and engaging clutch 12. Again, Fig. 4 (not shown), the embodiment of Figure 2 (not shown), is provided with a torque converter by-pass clutch 18, a blocking clutch 22 and a free-wheel (23) between the planet carrier (17) and the gear-box casing. Operation is similar to that of the Figure 3 embodiment, but the torque converter is not utilized as a brake, the free-wheel (23) being bridged over by brake 11 during usual engine breaking in low speed gears. In Fig. 5 (not shown), a six-speed gear-box is obtained by arranging an additional intermediate planetary gear set in the Fig. 3 embodiment so that its ring gear (24) is connected to the output shaft 14, its sun gear (25) is connected to a brake (27), and its carrier (28) is connected to the ring gear 10 of the reduction planetary gear set, clutch 12 being engageable to lock sun gear (25) to carrier (28), and hence still clutch ring gear 10 to output shaft 14. The reduction planetary gear set is provided with stepped planets. The first, third, split-torque fifth and the first reverse coincide with the first, second, splittorque third, and reverse of the Fig. 3 embodiment respectively. Second and fourth are derived from first and third respectively by releasing brake 11 and engaging brake (27). An all-mechanical fifth is provided by engaging clutch 22. Second reverse is derived from first reverse by disengaging clutch 12 and engaging brake (24). The torque converter is utilized for braking in four stages, the first, second and fourth coinciding with first, second and third of the Fig. 3 embodiment, and the third stage being derived from the second by disengaging clutch 12 and engaging brake (27). A five-speed gear-box is derived from the Fig. 5 embodiment by omitting second and suitably selecting first, the reduction gear set having simple planets. A seven-speed gear-box is obtained from the Fig. 5 embodiment by braking the sun gear 15 to provide another (lowest) speed, the output shaft 14 driving a final output shaft (32) parallel thereto through gears (30), (31). Practical ratios are described for the gearboxes of Figs. 3, 4 and 5, e.g. for buses. The Fig. 3 embodiment may be automatically controlled with start in second, and 2-1 kickdown shift, or start in first with all shifts being automatic. In the latter, the clutch 22 may be mounted on a free-wheel. In the Fig. 5 embodiment only the second, fourth and fifth speeds are automatically shifted, or all gears may be shifted semi-automatically.